A honeycomb structure has been used in a filter for trapping particulate matter in exhaust gas from an internal combustion engine, boiler, and the like, particularly diesel particulate matter.
Heretofore, as an extrusion die for a ceramic honeycomb body, for example, there has been known the extrusion die (10) for a honeycomb body shown in FIGS. 4 and 5, which is provided with groovy slits (2) on the front face of a base metal made of stainless steel and iron, the groovy slits being formed by cell blocks, and provided with back holes (4), on a back face thereof, each communicatively connected with the slit (2).
At the time, when a honeycomb segment is extruded using, for example, a die having a square honeycomb structure (in particular, when a honeycomb segment whose outer wall thickness is not large is extruded), if the number of cell blocks per one side is odd number, design of cell blocks 3 and back holes 4 is not appropriate particularly at corner portions 7. Accordingly, when the honeycomb segment is extruded by a die jig shown in FIG. 6, a kneaded clay extrusion speeds is made uneven at slits, from which strain is generated on an extruded face (pattern) of an extruded body and the extruded body (the formed body) is bent.
Further, when the cell blocks 3 are formed at right angle at the corner portions 7 as shown in FIG. 2, flow of kneaded clay is deteriorated. Accordingly, concavo-convex portions may be formed on an extruded face of a resultant extruded body (honeycomb segment), and fine splits 40 may be generated on an outer wall as shown in FIG. 7(b).
The present invention is made in view of the above described problems heretofore, and aims to provide an extrusion die for a honeycomb body, which is possible to reduce strain generated on an extruded face of an extruded body after extrusion, possible to maintain a stable frictional force of extrusion, excellent in extrudability, and excellent in wear resistance.